1. Field of the Invention
The present invention relates to a disk player which plays disks such as a mini disk (MD) and a compact disk (CD).
2. Description of Background Information
For disks on which digital audio data is recorded, conventional mini disk players are configured to write temporarily, in a playback mode, data read by the pickup, into a memory via an EFM (Eight to Fourteen Modulation) decoder, and then reads the data written in the memory in the writing order at a speed slower than the writing speed. The read data is sent through an audio compression decoder and a D/A (Digital/Analog) converter to be output as an analog audio signal. The address of each sector on a disk like a mini disk is written at the header portion in that sector, and data is read sector by sector, which is a unit of data block, in accordance with the addresses, i.e., data is read address by address. The data in the memory which has been read is to be erased.
When data cannot be read from a disk or read data is in error, the reading operation is performed again or a retry operation is executed starting at the address whose data has not been correctly read. Unless correct data is written in the memory, this retry operation continues until the amount of remaining data already written in the memory becomes equal to or smaller than a given value.
When the amount of remaining data in the memory becomes equal to or smaller than the given value, the retry operation is stopped and a new data reading operation is executed at the next address whose data is readable.
FIG. 1 illustrates such a reading operation in the form of a control flowchart for a system controller in a mini disk player. The system controller instructs the reading of data at an address N on a disk (step S1) and determines if this data reading operation has been carried out (step S2). When the data reading operation has been executed, the system controller determines if the data read from the disk (or the read data) is correct (step S3). Since the EFM decoder detects an error in the read data by the CIRC (Cross Interleave Reed-Solomon Code), the system controller can determine if the read data is correct from the result of that detection. When the read data is correct, the system controller instructs the writing of the read data into the memory (step S4), and determines if a program to be played back has been completed (step S5). When the program to be played back has not ended, the address N on the disk is incremented by "1" and the resultant address is set as a new address N (step S6) after which the flow returns to step S1. When the program to be played back has ended, this routine is terminated.
The instruction to read data at the address N in step S1 is associated with the amount of remaining data in the memory. When data which is equal to or greater in amount than a predetermined value A has not been read into the memory and there is therefore some data remaining in the memory, the control by the system controller is in a pause mode. When the amount of remaining data becomes equal to or smaller than a predetermined value B (A&gt;B), the pause mode is released and the data reading operation is to be actually instructed.
When it is determined in step S2 that the data reading operation has not been executed, the system controller determines if the amount of remaining data in the memory is equal to or greater than a predetermined value X (B&gt;X) (step S7). When the read data is determined to be in error in step S3, the flow also proceeds to step S7. When the amount of remaining data in the memory is equal to or greater than the predetermined value X in step S7, the system controller allows the pickup to search for the address N (step S8), and then the processing returns to step S1 to read data at the address N. When the amount of remaining data in the memory is smaller than the predetermined value X, on the other hand, the system controller causes the pickup to jump the addresses to search for an address whose data is readable (step S9), and sets this address as the address N (step S10) after which the system controller returns to step S1.
The part (a) in FIG. 2 indicates the data recorded positions that are specified by addresses N-2, N-1, N, . . . , and N+m on a disk. In the illustrated case, correct data is not readable in the range from the address N to the address N+m-. The part (b) in FIG. 2 indicates the chronological flow of the operation by the pickup to access at the data recorded positions in the part (a) in FIG. 2 in accordance with the operation illustrated in FIG. 1.
FIG. 3 shows the relationship between the chronological operational flow illustrated in FIG. 2 and the amount of remaining data in the memory. After a pause mode b is released at an earlier address than the address N-2, a data reading operation a is performed up to the address N-2. When data accumulated amounts to the predetermined value A which is close to the memory capacity, no further data can be written in the memory so that the disk player enters the pause mode. When the amount of data in the memory is reduced to the predetermined value B, the data reading operation starts again. After the data reading operation for the address N-2 is completed, the pause mode b is temporarily started and then the data reading operation starts again. When the data read position reaches the address N, the reading operation cannot be performed properly so that the address N is detected by a searching operation c after which the reading operation a for the address N starts again. If the data at the address N is not actually readable, a retry operation is performed to repeat the data reading operation a and the searching operation c. When the amount of remaining data in the memory becomes smaller than the predetermined value X, the reading operation a for the address N is interrupted and a jumping operation d takes place to search out an address whose data is readable. When the address N+m is detected as the address whose data is readable as illustrated, the data reading operation a starts.
When the amount of remaining data in the memory becomes smaller in the retry operation and some cause like vibration occurs to inhibit the reading operation then, this conventional mini disk player cannot read the address whose data is actually readable, before the memory becomes empty. This results in a sound failure, causing an unpleasant listening condition. This problem is not inherent to mini disk players alone, but it is rather common to the other conventional disk players including a compact disk player, which have a memory for temporary storage of data read from a disk by the pickup in a playback mode and execute a retry operation when data reading is failed.